Which preposition to use with underminers

of Occurrences 3%

And I fell asleep thinking that parents have a duty to children greater than children to parents, and they who do not fulfil their responsibility in this respect are as bad in their morals as a debauchee, corrupt the community as much as a thief, and are among the ablest underminers of their nation.

among Occurrences 1%

When will the cause of learning cease to have assailants and underminers among those who profess to serve it?

Which preposition to use with  underminers